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Thread: Adding 12V AC Outlets...

  1. #21
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    I make a custom switch in my power inverter. Car starts, inverter start, Car off inverter off. Also I put a bypass in between the inverter. If interested I can tell you what I did. PM me.

  2. #22
    Raw Wave
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    A $5 relay connected to IGN or the alternator's charge lamp circuit?

  3. #23
    Constant Bitrate leo_bergamo's Avatar
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    Quote Originally Posted by DevonZ View Post
    Also, I was looking at inline fuses and found a 30A one that had 12 gauge wiring (estimate) on the ends... Would this defeat the purpose of using a 6 gauge wire?

    Is there an online site with good prices on wiring? All of the sites I've found don't look very well established or trustworthy.
    You can usually find the inline fuses at Walmart or the like near their car audio department. The previously mentioned amp kit is a great idea also. The main reason for the inline fuse at the battery is if at any point the positive wire's coating is stripped away after the inline fuse it will more than likely short on the firewall and or other ground sources in the engine compartment. If that is too occur that power wire can draw huge amperage from the battery and hence burn the wire up and set plastic or any other combustible sources near the wire a blaze, trust me I am speaking from experience I set an Chevy Astro van on fire.

    You should also take into consideration that the nature of AC voltage and it's methods of application and precautions is a different school of thought than with DC voltage. Some simple examples would be AC amperage is different then DC amperage, AC fuses differ from DC fuses and stranded wire and solid wire have different applications with each type of voltage. Their are numerous examples.

    I do not mean to sound like a "know-it-all" some super experienced electrician which I am not but I have been were you are wondering the possibilities and when I attempted something I set a vehicle ablaze because when you make a mistake with electricity in general especially high voltage it is very unforgiving.

  4. #24
    Raw Wave
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    Quote Originally Posted by leo_bergamo View Post
    AC fuses differ from DC fuses and stranded wire and solid wire have different applications with each type of voltage...
    It depends what you mean.....

    There is no else little difference in AC or DC fuses in respect to current - and fuses etc are current devices (not voltage).
    However each type is voltage rated for a max voltage - say 250VAC & 80VDC (so the interrupted voltage doesn't jump the break, or the fuse-holder insulation, etc).

    If you mean that a 100W inverter has over 10A input current @12V but under 1A or output current (@110VAC or above), then yes - there is that "voltage multiplication" factor.


    As to AC being different wrt DC regards safety and application, it isn't really. Not that many would necessarily understand that.
    [For example - 2 questions: (1) which is safer - 100VAC or 100VDC; (2) Which is easier to interrupt - 10A AC or 10A DC?]

    But people tend to think of DC as being low voltage, and AC as high. Hence the confusion.

    Many also seem to think AC in a vehicle is MORE dangerous than a domestic supply (mains, wall socket etc).
    In fact it is usually safer because you can usually touch EITHER side of the AC output and NOT get shocked. but that depends on GND or Earth referencing etc.
    But these days that is easily overcome with RCDs.


    PS - I wouldn't expect an inverter output to be fused as that is handled by the inverters own (DC) fuse or other input fuse.
    Output fusing would probably only be done on large inverters where load discrimination is required - eg, a PC and monitor to the same inverter; if the monitor faults, blow its fuse BEFORE the main fuse blows, hence keeping the PC alive. (As to doing that - good luck! But in the days of CRT displays, separate inverters and UPS were recommended anyhow - one for monitors (and motors etc) & others for PCs, modems etc.)

  5. #25
    Constant Bitrate leo_bergamo's Avatar
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    Someone once told me experience teaches caution it is upon you if you learn. I learned enough from my dablings with low and high voltage voltage and current. Just trying to express that this subject should not be taken lightly.

  6. #26
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    I totally agree.

    Sorry - I wasn't trying to counter the hazard.
    But I wanted to prevent misunderstanding - I get sick of people asking for a 12V fuse, or saying they can't use their 10A 250VAC 3AG fuse in their older 12V vehicle.


    It's the nature of the supply that makes it hazardous.
    A 12V car make have a non-lethal voltage, but ever watch a few hundred or thousand Amps short in one (that won't happen in a domestic AC supply), or its battery explode?


    And many people still get it wrong - what is most hazardous, high voltage AC or DC (eg, 80V and above)?
    And of interest, which is harder to interrupt (fuse etc) - AC or DC?

  7. #27
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    Quote Originally Posted by OldSpark View Post
    And many people still get it wrong - what is most hazardous, high voltage AC or DC (eg, 80V and above)?
    And of interest, which is harder to interrupt (fuse etc) - AC or DC?
    High volt DC is definitely more dangerous haha. It is also extremely difficult to stop.

    In my noob/experimentation days, I decided to test a 150 amp DC circuit breaker. To test it I used a huge deep cycle/truck starting battery. I grabbed a pair of jumper cables, and attached the breaker to the battery in the same situation as a short. I monitored the cables with a clamp on current meter. Needless to say 900+ amps were flowing through that cable and the breaker didn't trip. After 15 seconds I actually disconnected it as the cables were changing color.
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  8. #28
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    LOL!
    That sounds more like a faulty breaker, though many fail to realise the fuse or breaker's trip curve - eg, 110% all day, 150% for 1 hour, 200% for 2 minutes etc etc.


    Aside form that, I was getting at the "non-zero crossing" nature of DC. In simple terms...
    Sufficient voltage will jump a gap. (Eg - more than a few volts.)
    Once jumped, an arc forms and maintains the current flow.
    Switches and circuit breakers break current by separating 2 contacts.
    When separating, and arc can form.
    For AC currents, when the voltage crosses 0V, the current flow stops, the arc is extinguished, and it doesn't reform (assuming a big enough & clean gap).
    But DC never drops to zero.... hence the arc never stops....

    In practice, technology overcomes a lot of the above (contact platings; separation speed; dielectric insertions) but there are limits.
    Large DC supplies are simply not interrupted - eg, telephone exchanges, elecro-platers, DC power links, though some can be interrupted at the AC side (electroplaters, DC power links).
    Others - like telco's - simply burn to the ground if there is a bad short.

    AFAIR, 3,000 Amps DC was a "practical" upper breaking limit. 6kA was "explosive".

    Whilst DC fuses & breakers up to ~100A are no problem, they can get hairy above that.
    I love watching cheap 400A breakers burn their cars down (taking the audio system with it).

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